Piezomagnetism and magnetoelastic memory in uranium dioxide

Area of Science:

• Solid State Physics
• Materials Science
• Nuclear Engineering

Background:

• Uranium dioxide is a key nuclear fuel with complex thermal and magnetic properties.
• Its cubic structure features a 3-k non-collinear antiferromagnetic state and Jahn-Teller distortions.
• Strong coupling between magnetism and lattice vibrations creates a long-standing puzzle.

Purpose of the Study:

• To investigate the magneto-elastic properties of uranium dioxide single crystals.
• To understand the relationship between magnetic fields, lattice distortions, and piezomagnetism.
• To characterize the observed magneto-elastic memory effect.

Main Methods:

• Subjecting uranium dioxide single crystals to strong magnetic fields along threefold axes.
• Measuring linear magnetostriction and observing lattice distortions.
• Proposing a theoretical model incorporating magnetic anisotropy, elastic, Zeeman, Heisenberg exchange, and magnetoelastic energies.

Main Results:

• Observed abrupt positive linear magnetostriction and trigonal distortion under magnetic fields.
• Demonstrated reversal of magnetostriction upon field reversal, indicating piezomagnetism.
• Identified a switching phenomenon at ±18 T, revealing a robust magneto-elastic memory.
• Confirmed uranium dioxide as the hardest known piezomagnet.

Conclusions:

• Uranium dioxide exhibits significant piezomagnetic behavior driven by its complex magnetic structure and interactions.
• The material possesses a robust magneto-elastic memory, crucial for potential applications.
• The proposed model successfully explains the observed phenomena, advancing the understanding of actinide materials.